In the case of applying pressure contact type semiconductor devices (press pack semiconductor devices, for example) each composed of a multi-chip semiconductor device to a large capacity power conversion apparatus, in order to cool the pressure contact type semiconductor devices, a method is used in which the pressure contact type semiconductor devices and heat sinks are alternately stacked, and the pressure contact type semiconductor devices and the heat sink that have been alternately stacked are pressure-contacted and are cooled. When these are pressurized by base plates each composed of a flat pressurizing body as this pressurizing method, there may be a case in which since a pressurizing area thereof is large, unbalanced load that pressure is partially unbalanced is generated when the pressurizing surface is not flat, or the adhesiveness thereof is not good. In order to prevent this, a central portion of a press pack semiconductor device is pressurized with a pressurizing surface of a spherical shape, and thereby the unbalanced load is prevented (Refer to Patent Document 1, for example.).
However, in the method of Patent Document 1, there has been a problem that since the central portion of a press pack semiconductor device is pressurized, the pressurized pressure is decreased from the central portion toward the outer circumferential surface, and thereby it is difficult to uniformly pressurize the press pack semiconductor device, and thermal destruction is easily generated at the outer circumferential surface portion of the press pack semiconductor device. As a method for preventive this, a press pack semiconductor device stack which pressurizes pressure contact type semiconductor devices and heat sinks shown in FIG. 7 has been considered.
FIG. 7 is a sectional view of a pressure contact type semiconductor device stack 200 according to a conventional art which has an effect for preventing thermal destruction of devices composing a pressure contact type semiconductor device at the outer circumferential surface. The pressure contact type semiconductor device stack 200 shown in the drawing has a configuration in which pressure contact type semiconductor devices 10 and water-cooled heat sinks 9 are alternately stacked, and metal fittings 7 for insulating plate arranged at the both ends are pressurized from the outside to the inside. The above-described metal fittings 7 for insulating plate (a collective term of the metal fittings 7a, 7b for insulating plate) have been subjected to counter boring in the both surfaces thereof. Pressure is also applied to the outer circumferential surface of the pressure contact type semiconductor device by performing counter boring. As a result of this, it is possible to prevent thermal destruction of the above-described devices at the outer circumferential surface of the pressure contact type semiconductor device (the press pack semiconductor device).
FIG. 8 shows a configuration of the multi-chip semiconductor device 10 as an example of the pressure contact type semiconductor device 10. Here, there may be a case to describe it as the pressure contact type semiconductor device 10 or the multi-chip semiconductor device 10 depending on the content of the description, but the description will be made assuming that they are the same ones. FIG. 8(1) is a plan view of the pressure contact type semiconductor device 10, and FIG. 8(2) is an A-A sectional view of the pressure contact type semiconductor device 10 shown in FIG. 8(1). The pressure contact type semiconductor device 10 shown in the drawing is provided with a notch portion 10b. In addition, the pressure contact type semiconductor device 10 is configured so that a plurality of chips 10a are arranged on the same plane.